Methods for operating ethylene oligomerization reactor systems with an integrated ultrasonic flow meter

Abstract

Methods for determining ethylene concentration in an ethylene oligomerization reactor using an ultrasonic flow meter are described, and these methods are integrated into ethylene oligomerization processes and related oligomerization reactor systems.

We claim: 
     
       1. An oligomerization reactor system comprising:
 (A) a reactor configured to contact a catalyst system with ethylene, an organic reaction medium, and optional hydrogen under oligomerization conditions to produce an oligomer product; 
 (B) one or more reactor inlets configured to introduce the catalyst system, ethylene, and the organic reaction medium into the reactor; 
 (C) a reactor discharge line configured to withdraw an effluent stream containing the oligomer product from the reactor; 
 (D) an analytical system configured to determine an ethylene concentration in the reactor and/or in the reactor discharge line, the analytical system comprising an ultrasonic flow meter; and 
 (E) a controller configured to control an ethylene flow rate of the ethylene into the reactor, a catalyst system flow rate of the catalyst system into the reactor, a reaction temperature, a reaction pressure, or any combination thereof, based on the ethylene concentration determined by the analytical system. 
 
     
     
       2. The system of  claim 1 , wherein the ultrasonic flow meter is integrated into the reactor. 
     
     
       3. The system of  claim 1 , wherein the ultrasonic flow meter is integrated into the reactor discharge line. 
     
     
       4. The system of  claim 1 , wherein the reactor comprises a loop reactor. 
     
     
       5. The system of  claim 1 , wherein the reactor and the ultrasonic flow meter are configured to operate at a temperature in a range from 60° C. to 115° C. and a pressure in a range from 400 psig to 1500 psig. 
     
     
       6. The system of  claim 1 , wherein the one or more reactor inlets are further configured to introduce hydrogen into the reactor. 
     
     
       7. The system of  claim 1 , wherein the catalyst system comprises a heteroatomic ligand chromium compound complex and an organoaluminum compound, or a heteroatomic ligand, a chromium compound, and an organoaluminum compound. 
     
     
       8. The system of  claim 1 , wherein:
 the ultrasonic flow meter is integrated into the reactor; and 
 the ultrasonic flow meter comprises a length of pipe integrated into the reactor, wherein the ultrasonic flow meter has a same inside diameter as the reactor. 
 
     
     
       9. The system of  claim 1 , wherein:
 the ultrasonic flow meter is integrated into the reactor discharge line; and 
 the ultrasonic flow meter comprises a length of pipe integrated into the reactor discharge line, wherein the ultrasonic flow meter has a same inside diameter as the reactor discharge line. 
 
     
     
       10. The system of  claim 1 , wherein the organic reaction medium comprises an aliphatic hydrocarbon. 
     
     
       11. A process for operating an oligomerization reactor system, the process comprising:
 (I) contacting ethylene, an organic reaction medium, optionally hydrogen, and a catalyst system comprising a heteroatomic ligand chromium compound complex and an organoaluminum compound, or a heteroatomic ligand, a chromium compound, and an organoaluminum compound, in a reactor within the oligomerization reactor system to form an oligomer product; 
 (II) discharging an effluent stream containing the oligomer product from the reactor through a reactor discharge line; 
 (III) determining an ethylene concentration in the reactor discharge line by:
 (i) flowing the effluent stream through an ultrasonic flow meter integrated into the reactor discharge line; 
 (ii) determining a speed of sound in the effluent stream from the ultrasonic flow meter; and 
 (iii) correlating the speed of sound to a standard to determine the ethylene concentration in the reactor discharge line; and 
 
 (IV) adjusting an ethylene flow rate of the ethylene into the reactor, a catalyst system flow rate of the catalyst system into the reactor, a reaction temperature, a reaction pressure, or any combination thereof, when the ethylene concentration has reached a predetermined level; 
 wherein the ultrasonic flow meter comprises a length of pipe integrated into the reactor discharge line. 
 
     
     
       12. The process of  claim 11 , wherein:
 the process has an ethylene conversion in a range from 40 to 80 mol %; and 
 a linear velocity of the effluent stream through the ultrasonic flow meter is in a range from 0.5 to 20 ft/sec. 
 
     
     
       13. The process of  claim 11 , wherein the effluent stream comprises ethylene, the organic reaction medium, optionally hydrogen, the oligomer product, and activated or deactivated catalyst system components. 
     
     
       14. The process of  claim 13 , wherein the effluent stream contains:
 from 6 to 25 wt. % ethylene; 
 from 40 to 70 wt. % organic reaction medium; and 
 from 15 to 30 wt. % oligomer product. 
 
     
     
       15. The process of  claim 14 , wherein the oligomer product contains C 4 + hydrocarbons and a total amount of C 6  olefins and C 8  olefins of at least 65 wt. %, based on the oligomer product. 
     
     
       16. The process of  claim 11 , wherein the oligomer product is formed at:
 a reaction temperature in a range from 60° C. to 115° C.; and 
 a reaction pressure in a range from 400 psig to 1500 psig. 
 
     
     
       17. The process of  claim 16 , wherein:
 the reaction temperature is adjusted in step (IV); or 
 the reaction pressure is adjusted in step (IV); or 
 both. 
 
     
     
       18. The process of  claim 11 , wherein:
 the ethylene flow rate is adjusted in step (IV); or 
 the catalyst system flow rate is adjusted in step (IV); or 
 both. 
 
     
     
       19. The process of  claim 11 , wherein the standard comprises a calibration curve. 
     
     
       20. The process of  claim 11 , wherein the step of correlating comprises a mathematical model. 
     
     
       21. The process of  claim 11 , wherein the reactor comprises a loop reactor. 
     
     
       22. The process of  claim 11 , wherein the reactor comprises a stirred tank reactor.